late 14c., "a circumference; a periphery, a line going around (an area), whether circular or not; a circular or circuitous course," from Old French circuit (14c.) "a circuit; a journey (around something)," from Latin circuitus "a going around," from stem of circuire, circumire "go around," from circum "round" (see circum-) + ire "to go" (from PIE root *ei- "to go").
From c. 1400 as "space enclosed within certain limits." Hence, "district in which any business involving periodic journeys is done (1570s), especially of judicial assignments involving the journey of a judge from one place to another; in reference to routes followed by itinerant entertainers from 1834. Hence also circuit-rider "Methodist minister who rides a circuit, preaching successively in different stations" (by 1834); to ride circuit "take a roundabout course" is from 1650s.
Electrical sense "arrangement by which a current is kept up between two poles" is from 1746. Circuit-breaker "device for automatically opening an electrical circuit" is recorded from 1874. Related: Circuital.
"going round in a circuit, indirect," 1660s, from Medieval Latin circuitus "full of roundabout ways," from Latin circuitus "a going round" (see circuit (n.)). Related: Circuitously; circuitousness.
also *ker-, Proto-Indo-European root meaning "to turn, bend."
It forms all or part of: arrange; circa; circadian; circle; circuit; circum-; circumcision; circumflex; circumnavigate; circumscribe; circumspect; circumstance; circus; cirque; corona; crepe; crest; crinoline; crisp; crown; curb; curvature; curve; derange; flounce (n.) "deep ruffle on the skirt of a dress;" krone; ring (n.1) "circular band;" ranch; range; ranger; rank (n.) "row, line series;" research; recherche; ridge; rink; rucksack; search; shrink.
It is the hypothetical source of/evidence for its existence is provided by: Latin curvus "bent, curved," crispus "curly;" Old Church Slavonic kragu "circle;" perhaps Greek kirkos "ring," koronos "curved;" Old English hring "ring, small circlet."
It forms all or part of: Abitur; adit; ambience; ambient; ambit; ambition; ambitious; andante; anion; cation; circuit; coitus; commence; commencement; concomitant; constable; count (n.1) title of nobility; county; dysprosium; errant; exit; initial; initiate; initiation; introit; ion; issue; itinerant; itinerary; janitor; January; Janus; Jena; Mahayana; obiter; obituary; perish; praetor; Praetorian; preterite; sedition; sudden; trance; transient; transit; transitive; viscount.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit e'ti "goes," imas "we go," ayanam "a going, way;" Avestan ae'iti "goes," Old Persian aitiy "goes;" Greek ienai "to go;" Latin ire "to go," iter "a way;" Old Irish ethaim "I go," Irish bothar "a road" (from *bou-itro- "cows' way"), Gaulish eimu "we go;" Lithuanian eiti "to go;" Old Church Slavonic iti "go;" Bulgarian ida "I go;" Russian idti "to go;" Gothic iddja "went."